The OEIS is supported by the many generous donors to the OEIS Foundation.

 Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 59th year, we have over 358,000 sequences, and we’ve crossed 10,300 citations (which often say “discovered thanks to the OEIS”). Other ways to Give
 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A061860 Variant of A061417. 2
 1, 2, 4, 11, 28, 152, 726, 5268, 40438, 365944, 3628810, 39974466, 479001612, 6228256404, 87178339984, 1307706805928, 20922789888016, 355688409760972, 6402373705728018, 121645133931170028, 2432902008232456692 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS Does this count some variety of necklaces? LINKS G. C. Greubel, Table of n, a(n) for n = 0..445 FORMULA a(n) = (1/n)*Sum_{d|n} phi(n/d)*C(n, d)*(d!). MAPLE [seq(A061860(j), j=1..40)]; with(numtheory); A061860 := proc(n) local d, s; s := 0; for d in divisors(n) do s := s + phi(n/d)*(binomial(n, d))*(d!); od; RETURN(s/n); end; MATHEMATICA a[n_] := DivisorSum[n, EulerPhi[n/#] Binomial[n, #] (#!)&]/n; Array[a, 25] (* Jean-François Alcover, Mar 06 2016 *) CROSSREFS A061860[p] = A061417[p] = (p-1)!+(p-1) for all prime p's. Sequence in context: A005503 A148139 A336871 * A093960 A267912 A118311 Adjacent sequences: A061857 A061858 A061859 * A061861 A061862 A061863 KEYWORD nonn AUTHOR Antti Karttunen, May 11 2001 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified December 5 15:27 EST 2022. Contains 358588 sequences. (Running on oeis4.)